Solvent dewaxing process for lubricating oils



Patented Dec. 27, 1938 UNITED STATES SOLVENT DEWAXING PROCESS FOR LUBRIOATING OILS Horace B. Setzler, Cofieyville, Kans., assignor to The National Refining Company, a corporation of Ohio No Drawing. Application October 8, 1934, Serial No. 747,421

2 Claims.

This invention relates to petroleum oil-refining processes, and more especially to a solvent process for the removal of amorphous wax from waxcontaining oils and is designed as an improvement over the solvent process disclosed in United States Letters Patent No. 1,791,329 to Horace B. Setzler and Mert C. McDonald, dated February 3, 1931, so that paraffinic and mixed base oils, deficient in asphaltic or unsaturated compounds, may be successfully dewaxed by the solvent properties of sulphuric acid. The process of said patent cannot be successfully applied to aparaninic or other oil in which the concentration of unsaturated or asphaltic hydrocarbons is insufficient for a proper reaction with the acid, consequently the amorphous wax will not be precipitated with the sludge, but will remain in the stock.

A further object of the present invention is to carry the working temperatures to a lower degree than in said patent to insure that with the paraffinic or mixed base stock, substantially all of the wax may be removed to produce oils having a low pour test, if desired, or any higher range of pour test, at the election of the refiner.

I have found that by adding to a paraflinic or similar stock, an unsaturated or asphaltic hydrocarbon compound, then, diluting the mixture with kerosene, gasoline, naphtha or the like for handling at low temperatures and. to insure complete penetration of the acid, as will hereinafter appear, and then subjecting the combined mixture to sulphuric acid treatment, that the mixture can be substantially totally dewaxed, or the dewaxing can be stopped at any desired point, to produce the desired pour test.

It has also been found that the lubricating value. of the asphaltic compound added to the paraiiinic or mixed base stock, is raised by the process, and that the total resulting product has a lower pour test, is of better color and odor,

vary from about 5% to 40% of the volume of the parafiinic stock to be treated, depending on the concentration of asphaltic compounds in the material being added. After this determination has been made, the parafiinic stock, such as a bright stock or long residuum from a Pennsylvania crude, and the asphaltic stock are thoroughly mixed in any suitable way, a more thorough and quicker mixing being effected if the oils are held at between 90 and 120 F., during the mixing operation. During the mixing of the oils or subsequently thereto, depending on the mixing temperature, any suitable diluent, such as kerosene, gasoline, coal tar benzene, naphtha, or the like, is preferably added to constitute around 40% or 50% of the total volume of oils to be processed. The diluent is added as a means of increasing the liquidity of the product for better penetration by the sulphuric acid and to maintain liquidity when chilled, so that it may be more readily transferred and agitated.

The mixture is now ready for treatment in apparatus such as that disclosed in the patent above-identified or any other suitable apparatus. The mixture is, therefore, passed through any suitable refrigerating or chilling equipment, such as a Carbondale or equivalent chiller, and its temperature is lowered to in the neighborhood of from to F., as determined by the pour test desired in the ultimate product. If the stock being treated and the added asphaltic oil are to be entirely cleared of wax, it will be found that the mixture should be lowered to from -10 to -20 F.

The chilled oil is now delivered through an insulated transfer pipe to an insulated agitator, which may, if desired, be provided with refrigerating or cooling coils to maintain the low temperature during agitation with sulphuric acid. The agitator may be of any suitable or preferred type, and while the oil is held at low temperature and is being constantly agitated, a calculated quantity of sulphuric acid of 66 Baume, or stronger, such as oleum, is added in about the proportions of 20 to pounds of acid to each barrel of oil, including the diluent which has been added. The agitation is continued for a sufficient length of time to insure that the acid has thoroughly and completely penetrated throughout the volume of the chilled mixture and has contacted and reacted with all of the asphaltic, unsaturated and undesirable hydrocarbons in the oils.

- Agitation is then stopped, and. it will be found that within a relatively'short time,'usua1ly within about fifteen minutes, the acid sludge and the wax will he suddenly and decidedly settled or her. The clarified and purified oil may be drawn off the top of the agitator and treated in any suitable way to neutralize anyacid trace, and it may then be distilled for the removal and recovery of the diluent. The oil remaining in the still will be the finished bright stock or long residuum or lubricating oil, and it usually needs only a very light straining through fullers earth to be ready for the market. The sludge in the bottom of the agitator may be removed and treated in any desired way for the recovery of the amorphous wax or petrolatum.

Although it is impracticable to give detailed instructions for the dewaxing of every possible parafi'inic or mixed base stock to which the present process may be applicable, in general, it may be said that the percentage of the who-1e of asphaltic hydrocarbons to be added, will vary in accordance with the concentration of asphaltics or unsaturates in the added material. The higher the concentration, the smaller the volume of the material which Will'have to be added to the stock to be treated. The following table indicates some of the proportions in which the two materials have beenmixed:

Percent Pennsylvania bright stock to Lima tar 15 to 25 gravity 5to 15 Pennsylvania bright stock 85 to 95 Mid-Continent asphalt oil, 10 to 20 gravity 5 to 15 Pennsylvania bright stock 60 to 75 Mid-Continent fuel oil, 25 to 28 gravity- 25 to 40 The asphaltic compound may be of any suit able nature, such as those from Texas, South American and Mid-Continent crudes, Lima tars and the like, natural asphalts, fuel and road oils, pressure still bottoms, and residuums having asphalt content. Any low grade cheap oil of asphaltic or mixed base, reacting with sulphuric acid may be used.

The diluent used may be of any suitable char-- kerosene, gasoline,

The quantity'of acid is calculated tosupply from 20 to 30 pounds of 'acid to the barrel of oils being treated, plus the diluent.

By way of example, a specific run of 2400 barrels will bedescribed. 1075'barrels of cylinder stock made'from a Pennsylvania steam refined crude and barrels of an asphalt oil made from Mid-Continent crude, are mixed as here tofore described, and 1200 barrels of naphtha are added thereto, the proportions thus being:

' Percent Pennsylvania cylinder oil 45. 0 Asphalt oil 5.10 Naphtha 50.0

By the use of refrigerating equipment having about the capacity of 200 tons per day, When the outside temperature is around '80" F., the 2400 barrels may be reduced from around 80 to 100 down to around 0 F., in about 24 hours, and refrigeration is continued until the mixture leaves the chillers at about the rate of. 100 barrels per hour at a temperature of, around ,10 F., or the,

solvent action of the acid.

precipitated to the bottom of the agitating cham-' temperature may be taken down to around 20 F., and'is discharged into the agitator or mixing tank. At the end of the run, the material in the agitator will not have lost more than 2 or 3 degrees. It Will be understood that the lower the temperature at the time of sulphuric acid treatment, the lower the pour point of the finished lubricating-oil. With a -10 to 20 F., temperature, the pour point of the finished product 1 will be around 0 F. to 15 F.

While the oil is being held at its chilled temperature, the sulphuric acid is gradually added, at such a rate that within about one hour from 20.to 30 pounds of acid to the barrel of oil has been added, in the present instance from 48,000 pounds to 72,000 pounds. Agitation is then continued for about one hour to insure that all of the unsaturated asphaltic and undesirable hydrocarbons of the oils have been subjected to the Agitation is then stopped and it will be found that within about fifteen minutes all of the sludge carrying'the undesirable hydrocarbon compounds, will settle to thebottom of the agitator and will carry down with it substantially all of the amorphous wax contained within all of the oils in the material being treated. The clarified and purified oil and the sludge may now' be separately withdrawn and treated in any desirable way as heretofore indicated.

Paraffinic Asphaltic Finished stock stock oil Gravity, A. P I 27.7 18. 2 27.1 Flash 565 430 555 Fire 640 600 635 Viscosity 210 F., Saybolt 143 395 145 Pour 70 50 10/15 Color Olive green .Tet black Color, N. P. A. 5 Viscosity index 102 Conradson carbon, percent.-. 1.86 8. 1 1.0

The process was also carried out with a cylinder oil stock refined from Pennsylvania crude, a Mid-Continent asphalt oil, and naphtha, the three being mixed in. the respective proportions of 40%, 10% and 50% respectively. The specifications of the original stocks and the finished lubricating oil were: a

' Parafiinic Asphaltic Finished ock stock oil Gravity, A; P. I 26. 5 20. 75 26, 7

Flash-.. 565 420 54 Fire 625 580 620 210 F., Saybolt 157 Pour 75 55 15/20 Oolor Green Color, N. P A i 5 4 Viscosity index 99. 4

Oonradson carbon, percent. 2. 25 5. 6 1.20

As an indication of the flexibility of the process for dewaxing, decolorizing and'reducing the color content, raising the viscosity index and removing undesirable hydrocarbons by the solvent;

action of sulphuric acid at low temperatures,

' the process was carried out with a steam refined stock made from a crude oil from the Marietta,

Ohio, field. The added asphaltic base was a two materials and diluent, naphtha, were mixed in the following proportions:

- Per cent Marietta steam refined stock 48 Lima tar 4 Naphtha 48 The specifications of the stock treated and of the ultimate product after the process of the invention had been applied, were:

It is to be understood that the above examples are not to be construed as limiting the process of the invention, as the extent of dewaxing and consequently the pour test of the ultimate product will be in proportion to the degree of refrigeration at the time of the acid treatment, and furthermore, that investigation of the parafiinic or mixed base oil will indicate the preferred quantity of asphaltic material which should be added to the stock to be treated, this quantity in turn depending upon theconcentration of asphaltic or unsaturated compounds in the added oil.

Having described my invention and an illustrative method of practicing the same, I claim as new and desire to secure by Letters Patent, together with such modifications thereof as may be made by those skilled in the art, the following:

1. In the simultaneous dewaxing and acid treating of mineral oil which contains an insufficient quantity of sludge forming substance, the steps comprising adding a quantity of still residue to such oil, chilling the resulting mixture to a temperature which causes wax to precipitate, treating the mixture while cold with sulphuric acid in a quantity to react with the still residue and oil to form a sludge adapted to aid separation of the wax from the oil, and separating simultaneously the sludge and precipitated wax from the treated oil.

2; In the simultaneous dewaxing and acid treating of mineral oil which contains an insuflicient quantity of sludge forming substance, the steps comprising adding an asp'haltic hydrocarbon compound to such oil, chilling the resulting mixture to a temperature which causes the wax to precipitate, treating the mixture while cold with sulphuric acid in a quantity to react with the asphaltic hydro-carbon compound and oil to form a sludge adapted to aid separation of the wax from the oil, and separating simultaneously the sludge and precipitated wax from the treated oil.

HORACE B. SETZLER. 

